scholarly journals On the absence of a beneficial role of Rh towards C C bond cleavage during low temperature ethanol electrooxidation on PtRh nanoalloys

2020 ◽  
Vol 875 ◽  
pp. 114229
Author(s):  
Justyna Piwowar ◽  
Adam Lewera
Keyword(s):  
Low Temperature ◽  
Bond Cleavage ◽  
Ethanol Electrooxidation ◽  
Beneficial Role

On the Lack of Beneficial Role of Rh Towards C-C Bond Cleavage During Low Temperature Ethanol Electrooxidation on Pt-Rh Nanoalloys

2018 ◽  
Author(s):  
Justyna Piwowar ◽  
Adam Lewera
Keyword(s):  
Low Temperature ◽  
Electrode Potential ◽  
Ethanol Oxidation ◽  
Bond Cleavage ◽  
Ethanol Electrooxidation ◽  
Co Stripping ◽  
Beneficial Role ◽  
Bond Scission ◽  
Oxidation Of Ethanol

Numerous reports in scientific literature claim the increased activity of Rh-containing systems towards C-C bond scission in electrocatalytic oxidation of ethanol at ambient temperatures. Due to the claimed C-C bond breaking ability, Rh-containing systems are intensively investigated and widely recognized as the most promising candidates as anode materials for ethanol-feed low temperature fuel cells. This study aims at verifying the claim of beneficial role of Rh towards C-C bond scission during low temperature ethanol electrooxidation on Pt-Rh nanoparticles. We determined that the surface-normalized amounts of CO<sub>2 </sub>produced during ethanol oxidation are comparable on Pt, Rh and Pt-Rh nanoalloys, and smaller than CO<sub>2</sub> amounts obtained on exactly the same electrode from oxidation of monolayer of adsorbed CO. The whole amount of CO<sub>2</sub> detected during ethanol oxidation, regardless of Rh presence, or lack of thereof, seems to come exclusively from oxidation of submonolayer of CO<sub>ads</sub> produced during dissociative adsorption of ethanol at low electrode potential, and its subsequent oxidation at sufficiently high electrode potential. Our work suggest that Rh-containing alloys are not more active towards C-C bond scission than pure Pt, and on both metals the mechanism of oxidation of ethanol to CO<sub>2</sub> proceeds via the submonolayer of CO<sub>ads</sub>, which limits the quantity of CO<sub>2</sub> produced from ethanol at room temperature to negligible amount. The higher activity of Rh-containing materials towards C-C bond scission claimed in literature was determined to be due to overinterpretation of selectivity data.<br>To characterized the samples we used techniques like XPS, TEM, and cyclic voltammetry. For drove a conclusions we compere amount of CO<sub>2</sub> detected in DEMS during ethanol oxidation reaction and so called CO stripping experiment. <br><br>

On the Lack of Beneficial Role of Rh Towards C-C Bond Cleavage During Low Temperature Ethanol Electrooxidation on Pt-Rh Nanoalloys

2018 ◽  
Author(s):  
Justyna Piwowar ◽  
Adam Lewera
Keyword(s):  
Low Temperature ◽  
Electrode Potential ◽  
Ethanol Oxidation ◽  
Bond Cleavage ◽  
Ethanol Electrooxidation ◽  
Co Stripping ◽  
Beneficial Role ◽  
Bond Scission ◽  
Oxidation Of Ethanol

Numerous reports in scientific literature claim the increased activity of Rh-containing systems towards C-C bond scission in electrocatalytic oxidation of ethanol at ambient temperatures. Due to the claimed C-C bond breaking ability, Rh-containing systems are intensively investigated and widely recognized as the most promising candidates as anode materials for ethanol-feed low temperature fuel cells. This study aims at verifying the claim of beneficial role of Rh towards C-C bond scission during low temperature ethanol electrooxidation on Pt-Rh nanoparticles. We determined that the surface-normalized amounts of CO<sub>2 </sub>produced during ethanol oxidation are comparable on Pt, Rh and Pt-Rh nanoalloys, and smaller than CO<sub>2</sub> amounts obtained on exactly the same electrode from oxidation of monolayer of adsorbed CO. The whole amount of CO<sub>2</sub> detected during ethanol oxidation, regardless of Rh presence, or lack of thereof, seems to come exclusively from oxidation of submonolayer of CO<sub>ads</sub> produced during dissociative adsorption of ethanol at low electrode potential, and its subsequent oxidation at sufficiently high electrode potential. Our work suggest that Rh-containing alloys are not more active towards C-C bond scission than pure Pt, and on both metals the mechanism of oxidation of ethanol to CO<sub>2</sub> proceeds via the submonolayer of CO<sub>ads</sub>, which limits the quantity of CO<sub>2</sub> produced from ethanol at room temperature to negligible amount. The higher activity of Rh-containing materials towards C-C bond scission claimed in literature was determined to be due to overinterpretation of selectivity data.<br>To characterized the samples we used techniques like XPS, TEM, and cyclic voltammetry. For drove a conclusions we compere amount of CO<sub>2</sub> detected in DEMS during ethanol oxidation reaction and so called CO stripping experiment. <br><br>

Promoted C–C bond cleavage over intermetallic TaPt3 catalyst toward low-temperature energy extraction from ethanol

2015 ◽  
Vol 8 (6) ◽  
pp. 1685-1689 ◽  
Author(s):  
Rajesh Kodiyath ◽  
Gubbala V. Ramesh ◽  
Eva Koudelkova ◽  
Toyokazu Tanabe ◽  
Mikio Ito ◽  
...  
Keyword(s):  
Low Temperature ◽  
Bond Cleavage ◽  
Catalytic Performance ◽  
Energy Extraction ◽  
Ethanol Electrooxidation

Intermetallic TaPt3 nanoparticles promote C–C bond cleavage in ethanol and exhibit much higher catalytic performance than traditional catalysts for the ethanol electrooxidation.

The role of vitamin D in metabolic and reproductive disturbances of polycystic ovary syndrome: A narrative mini-review

2020 ◽  
pp. 1-8
Author(s):  
Daniela Menichini ◽  
Gianpiero Forte ◽  
Beatrice Orrù ◽  
Giuseppe Gullo ◽  
Vittorio Unfer ◽  
...  
Keyword(s):  
Vitamin D ◽  
Polycystic Ovary Syndrome ◽  
Embryo Quality ◽  
Polycystic Ovary ◽  
Vitamin D Supplementation ◽  
Endometrial Receptivity ◽  
Metabolic Disturbances ◽  
Ovary Syndrome ◽  
Beneficial Role

Abstract. Vitamin D is a secosteroid hormone that plays a pivotal role in several metabolic and reproductive pathways in humans. Increasing evidence supports the role of vitamin D deficiency in metabolic disturbances and infertility in women with polycystic ovary syndrome (PCOS). Indeed, supplementation with vitamin D seems to have a beneficial role on insulin resistance and endometrial receptivity. On the other hand, exceedingly high levels of vitamin D appear to play a detrimental role on oocytes development and embryo quality. In the current review, we summarize the available evidence about the topic, aiming to suggest the best supplementation strategy in women with PCOS or, more generally, in those with metabolic disturbances and infertility. Based on the retrieved data, vitamin D seems to have a beneficial role on IR, insulin sensitivity and endometrial receptivity, but high levels and incorrect timing of administration seem to have a detrimental role on oocytes development and embryo quality. Therefore, we encourage a low dose supplementation (400–800 IU/day) particularly in vitamin D deficient women that present metabolic disturbances like PCOS. As far as the reproductive health, we advise vitamin D supplementation in selected populations, only during specific moments of the ovarian cycle, to support the luteal phase. However, ambiguities about dosage and timing of the supplementation still emerge from the clinical studies published to date and further studies are required.

Metal-Metal Cooperative Bond Activation by Heterobimetallic Alkyl, Aryl, and Acetylide PtII/CuI Complexes

2020 ◽  
Author(s):  
Shubham Deolka ◽  
Orestes Rivada Wheelaghan ◽  
Sandra Aristizábal ◽  
Robert Fayzullin ◽  
Shrinwantu Pal ◽  
...  
Keyword(s):  
Alkyl Group ◽  
Bond Activation ◽  
Bond Cleavage ◽  
Terminal Alkyne ◽  
Alkyl Aryl ◽  
Metal Metal ◽  
The Stability ◽  
Selective Formation ◽  
Organoplatinum Compounds

We report selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from electron-deficient tetraarylborate [B(ArF)4]- anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the role of Cu center acts as a binding site for alkyne substrate, while activating its terminal C-H bond.

Mechanisms of ATP to cAMP Conversion Catalyzed by the Mammalian Adenylyl Cyclase: A Role of Magnesium Coordination Shells and Proton Wires

2019 ◽  
Author(s):  
Bella Grigorenko ◽  
Igor Polyakov ◽  
Alexander Nemukhin
Keyword(s):  
Adenylyl Cyclase ◽  
Bond Cleavage ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Md Simulations ◽  
Coordination Shell ◽  
Energy Profile ◽  
One Step ◽  
Type V

<p>We report a mechanism of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) conversion by the mammalian type V adenylyl cyclase revealed in molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) simulations. We characterize a set of computationally derived enzyme-substrate (ES) structures showing an important role of coordination shells of magnesium ions in the solvent accessible active site. Several stable six-fold coordination shells of Mg<sub>A</sub><sup>2+ </sup>are observed in MD simulations of ES complexes. In the lowest energy ES conformation, the coordination shell of Mg<sub>A</sub><sup>2+ </sup>does not include the O<sub>δ1</sub> atom of the conserved Asp440 residue. Starting from this conformation, a one-step reaction mechanism is characterized which includes proton transfer from the ribose O<sup>3'</sup>H<sup>3' </sup>group in ATP to Asp440 via a shuttling water molecule and P<sup>A</sup>-O<sup>3A</sup> bond cleavage and O<sup>3'</sup>-P<sup>A</sup> bond formation. The energy profile of this route is consistent with the observed reaction kinetics. In a higher energy ES conformation, Mg<sub>A</sub><sup>2+</sup> is bound to the O<sub>δ1</sub>(Asp440) atom as suggested in the relevant crystal structure of the protein with a substrate analog. The computed energy profile initiated by this ES is characterized by higher energy expenses to complete the reaction. Consistently with experimental data, we show that the Asp440Ala mutant of the enzyme should exhibit a reduced but retained activity. All considered reaction pathways include proton wires from the O<sup>3'</sup>H<sup>3' </sup>group via shuttling water molecules. </p>

scholarly journals I Like the Way You Eat It: Lemur (Indri indri) Gut Mycobiome and Geophagy

2021 ◽  
Author(s):  
Luigimaria Borruso ◽  
Alice Checcucci ◽  
Valeria Torti ◽  
Federico Correa ◽  
Camillo Sandri ◽  
...  
Keyword(s):  
Plant Material ◽  
Soil Characteristics ◽  
Nutrient Supply ◽  
Fungal Species ◽  
High Concentration ◽  
Beneficial Role ◽  
Intimate Connection ◽  
Indri Indri ◽  
Lemur Species

AbstractHere, we investigated the possible linkages among geophagy, soil characteristics, and gut mycobiome of indri (Indri indri), an endangered lemur species able to survive only in wild conditions. The soil eaten by indri resulted in enriched secondary oxide-hydroxides and clays, together with a high concentration of specific essential micronutrients. This could partially explain the role of the soil in detoxification and as a nutrient supply. Besides, we found that soil subject to geophagy and indris’ faeces shared about 8.9% of the fungal OTUs. Also, several genera (e.g. Fusarium, Aspergillus and Penicillium) commonly associated with soil and plant material were found in both geophagic soil and indri samples. On the contrary, some taxa with pathogenic potentials, such as Cryptococcus, were only found in indri samples. Further, many saprotrophs and plant-associated fungal taxa were detected in the indri faeces. These fungal species may be involved in the digestion processes of leaves and could have a beneficial role in their health. In conclusion, we found an intimate connection between gut mycobiome and soil, highlighting, once again, the potential consequent impacts on the wider habitat.

Tannic Acid as a Natural Ferroptosis Inhibitor: Mechanisms and Beneficial Role of 3’‐ O ‐Galloylation

2021 ◽  
Vol 6 (7) ◽  
pp. 1562-1569
Author(s):  
Yangping Liu ◽  
Xican Li ◽  
Yujie Hua ◽  
Wenhui Zhang ◽  
Xianxi Zhou ◽  
...  
Keyword(s):  
Tannic Acid ◽  
Beneficial Role

The beneficial role of the synthetic microneurotrophin BNN20 in a focal demyelination model

2021 ◽  
Vol 99 (5) ◽  
pp. 1474-1495
Author(s):  
Ilias Kalafatakis ◽  
Alexandros Patellis ◽  
Ioannis Charalampopoulos ◽  
Achille Gravanis ◽  
Domna Karagogeos
Keyword(s):  
Beneficial Role ◽  
Focal Demyelination

scholarly journals Dissecting the Roles of Cuticular Wax in Plant Resistance to Shoot Dehydration and Low-Temperature Stress in Arabidopsis

2021 ◽  
Vol 22 (4) ◽  
pp. 1554
Author(s):  
Tawhidur Rahman ◽  
Mingxuan Shao ◽  
Shankar Pahari ◽  
Prakash Venglat ◽  
Raju Soolanayakanahally ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Low Temperature ◽  
Cold Acclimation ◽  
Water Loss ◽  
Cuticular Wax ◽  
Dehydration Stress ◽  
Wax Deposition ◽  
Cuticular Waxes ◽  
Gas Chromatography Mass Spectroscopy

Cuticular waxes are a mixture of hydrophobic very-long-chain fatty acids and their derivatives accumulated in the plant cuticle. Most studies define the role of cuticular wax largely based on reducing nonstomatal water loss. The present study investigated the role of cuticular wax in reducing both low-temperature and dehydration stress in plants using Arabidopsis thaliana mutants and transgenic genotypes altered in the formation of cuticular wax. cer3-6, a known Arabidopsis wax-deficient mutant (with distinct reduction in aldehydes, n-alkanes, secondary n-alcohols, and ketones compared to wild type (WT)), was most sensitive to water loss, while dewax, a known wax overproducer (greater alkanes and ketones compared to WT), was more resistant to dehydration compared to WT. Furthermore, cold-acclimated cer3-6 froze at warmer temperatures, while cold-acclimated dewax displayed freezing exotherms at colder temperatures compared to WT. Gas Chromatography-Mass Spectroscopy (GC-MS) analysis identified a characteristic decrease in the accumulation of certain waxes (e.g., alkanes, alcohols) in Arabidopsis cuticles under cold acclimation, which was additionally reduced in cer3-6. Conversely, the dewax mutant showed a greater ability to accumulate waxes under cold acclimation. Fourier Transform Infrared Spectroscopy (FTIR) also supported observations in cuticular wax deposition under cold acclimation. Our data indicate cuticular alkane waxes along with alcohols and fatty acids can facilitate avoidance of both ice formation and leaf water loss under dehydration stress and are promising genetic targets of interest.

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